// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_BASE_UPLOAD_ELEMENT_READER_H_
#define NET_BASE_UPLOAD_ELEMENT_READER_H_

#include <stdint.h>

#include "base/macros.h"
#include "net/base/completion_callback.h"
#include "net/base/net_export.h"

namespace net {

class IOBuffer;
class UploadBytesElementReader;
class UploadFileElementReader;

// An interface to read an upload data element.
class NET_EXPORT UploadElementReader {
public:
    UploadElementReader() { }
    virtual ~UploadElementReader() { }

    // Returns this instance's pointer as UploadBytesElementReader when possible,
    // otherwise returns NULL.
    virtual const UploadBytesElementReader* AsBytesReader() const;

    // Returns this instance's pointer as UploadFileElementReader when possible,
    // otherwise returns NULL.
    virtual const UploadFileElementReader* AsFileReader() const;

    // This function must be called before calling any other method. It is not
    // valid to call any method (other than the destructor) if Init() fails.
    // This method can be called multiple times. Calling this method after an
    // Init() success results in resetting the state (i.e. the stream is rewound).
    //
    // Initializes the instance synchronously when possible, otherwise does
    // initialization aynschronously, returns ERR_IO_PENDING and runs callback.
    // Calling this method again after a Init() success results in resetting the
    // state.
    virtual int Init(const CompletionCallback& callback) = 0;

    // Returns the byte-length of the element. For files that do not exist, 0
    // is returned. This is done for consistency with Mozilla.
    virtual uint64_t GetContentLength() const = 0;

    // Returns the number of bytes remaining to read.
    virtual uint64_t BytesRemaining() const = 0;

    // Returns true if the upload element is entirely in memory.
    // The default implementation returns false.
    virtual bool IsInMemory() const;

    // Reads up to |buf_length| bytes synchronously and returns the number of
    // bytes read or error code when possible, otherwise, returns ERR_IO_PENDING
    // and runs |callback| with the result. |buf_length| must be greater than 0.
    virtual int Read(IOBuffer* buf,
        int buf_length,
        const CompletionCallback& callback)
        = 0;

private:
    DISALLOW_COPY_AND_ASSIGN(UploadElementReader);
};

} // namespace net

#endif // NET_BASE_UPLOAD_ELEMENT_READER_H_
